1. Field of the Invention
The present invention relates to an optimal recording apparatus and method for optical recording media.
In particular, the present invention relates to an optimal recording apparatus and method for optical recording media which are capable of identifying a write strategy for an optimal recording of data on an optical recording medium, thereby allowing the identified write strategy to be utilized for a subsequent recording of data on the optical recording medium.
2. Description of the Conventional Art
FIG. 1 illustrates the configuration of a conventional optical recording/reproducing apparatus for recording data on an optical recording medium and reproducing the recorded data.
As shown in FIG. 1, this optical recording/reproducing apparatus includes a digital recording signal processing unit 30a for adding an error correction code (ECC) to input digital data, thereby converting the input digital data into a recording format, a channel bit encoder unit 40 for reconverting the data, converted into the recording format, into a bit stream, an optical driver unit 50 for outputting a light amount drive signal, an optical pick-up unit 11 for recording a desired signal onto an optical recording medium 10 in accordance with the light amount drive signal, and detecting a recording signal from the optical recording medium 10, and a drive unit 80 for driving the optical prick-up unit 11 and a motor M. The optical recording/reproducing apparatus further includes an R/F unit 60 for filtering a signal detected by the optical pick-up unit 11, conducting a waveform shaping for the filtered signal, and converting the resultant signal into a binary signal, a servo unit 70 for controlling the driving of the drive unit 80, based on signals indicative of tracking errors and focusing errors generated in the optical pick-up unit 11, along with the rotating speed of the optical recording medium 10, a digital reproduced signal processing unit 30b for recovering the binary signal into original data at a clock synchronizing with the binary signal, and a microcomputer 100 for controlling the recording/reproducing procedure.
Now, an operation of the conventional optical recording/reproducing apparatus will be described in conjunction with FIG. 1.
When a data recording request is inputted to the microcomputer 100 under the condition in which an optical recording medium 10 is loaded in a tray not shown, the optical recording/reproducing apparatus conducts an optimal power calibration (OPC).
In accordance with the OPC procedure, the microcomputer 100 controls the servo unit 70 and the drive unit 80 prior to recording of input data. In accordance with controlled operations of the servo unit 70 and drive unit 80, the optical pick-up unit 11 is controlled to read out a target writing power value Pind recorded in the form of 3-bit data W1, W2, and W3. FIG. 2 illustrates an example of the target writing power value recorded in the form of 3-bit data on the optical recording medium 10.
The microcomputer 100 then applies an adjustment signal to the optical driver unit 50 in a variable fashion. The adjustment signal is adapted to vary an optical power with reference to the read target recording power value, for example, 8 mW. FIG. 3 illustrates a variation in optical power with reference to a target recording power value. The optical driver unit 50 outputs a recording signal for test data at an optical drive power corresponding to the adjustment signal. In accordance with the recording signal, the optical pick-up unit 11 records test data onto a test recording area of the optical recording medium 10. FIG. 4 illustrates a recording signal test area A in a re-writable optical recording medium (CD-RW), along with a count area B for recording the number of test times.
The microcomputer 100 controls the pick-up unit 11 in a state, in which test data is recorded on the test area A of the optical recording medium 10, as shown in FIG. 4, in order to sequentially read out test data recorded several times. Each of the test data sequentially read is applied to the R/F unit 60 which, in turn, conducts a filtering and a waveform shaping for the test data, thereby reproducing that test data. FIG. 5 illustrates a reproduced signal for the test data recorded on the optical recording medium.
The microcomputer 100 then calculates the degree of modulation, based on the reproduced signal, and estimates a polynomial expression for a modulation degree curve (m=f(p)), using a curve filtering.
The modulation degree m corresponds to a value of I11T/ITOP (m=I11T/ITOP). Here, “I11T” represents the amplitude of the reproduced signal for an 11T signal, and “ITOP” represents a peak value of the 11T signal.
Next, a γ curve is derived using the estimated modulation degree curve “m=f(p)”.
FIG. 6 illustrates a modulation degree curve “m=f(p)” and a γ curve “γ=g(p)” for detecting an optimum recording power value. Here, an expression “γ=p/m×f′(p)” is established.
Also, the value of a target γ recorded on the optical recording medium 10 is read out. Based on the read target γ value, an optimum optical power is derived.
The microcomputer 100 controls the optical driver unit 50 to output, for the input data, a recording signal according to the optimum optical drive power detected in the above mentioned procedure. The optical drive unit 50 applies, to the optical pick-up unit 11, the recording signal according to the optical drive power, thereby allowing a pulse-width-modulated signal to be recorded onto a program area of the optical recording medium 10.
The microcomputer 100 also determines the format of the recording signal, that is, the pulse level and width of the recording signal, upon recording the input data, based on a write strategy recorded on the optical recording medium 10. FIG. 7 illustrates the optimum write strategy recorded on the optical recording medium 10. The data write strategy is recorded on the optical recording medium 10 in the form of a fixed value in the manufacture of the optical recording medium 10.
In the case of an once-writable optical recording medium, the data write strategy thereof has a value β, indicative of a signal non-linearity, fixed in accordance with the type of the recording medium. In the case of a re-writable optical recording medium, the data write strategy thereof has a value β fixed in accordance with the record speed of the recording medium. Accordingly, the input data is recorded onto the optical recording medium 10 after being converted into a recording signal, that is, recording pulses, at the calculated optimum recording power, based on the recording signal format.
As apparent from the above description, the write strategy recorded on an optical recording medium is an absolute value for the recording medium.
This means that the write strategy for an optical recording medium is set without taking into consideration the optical recorder used to record data onto the recording medium.
Meanwhile, recorders of different types may exhibit different recording circuit characteristics. Even in recorders of the same type, they may exhibit different recording circuit characteristics in accordance with different manufacturers thereof. For this reason, there are frequent occasions that although a request is made to record data on a recording medium in accordance with the write strategy set in the recording medium, that is, a pulse width and peak level set for one pit, it is impossible to output desired data having a signal format completely identical to the signal format set in the recording medium.
Nevertheless, in accordance with the conventional optimal data recording method, the recording of data corresponding to the signal format set in a recording medium is conducted, only based on an optimum recording power detected from the recording medium. For this reason, it may be impossible to record data on a recording medium under optimum recording conditions for the recording medium. Where signals recorded in such a state are reproduced, the resultant reproduced signals exhibit a jitter exceeding a tolerable range. Thus, there may be a degradation in the reproduction characteristics of recording data.